POllIFEHA (sponges). 
:37 
Eutaxicladina (Silurian to Jurassic) : desma with a 
thickened central node from which poceed three or more 
rays, expanded at the ends so as to join otliers (Jig- 12 A); 
chief genus, Astylospongia. Anomocladina (Jurassic to 
Recent) : desma a rod with swollen ends from which proceed 
three or more simple or branched rays, uniting as in Eutaxi- 
Fig. 12. — Fossil sponge spicules : Silicispongiae, Tetractinellida. Skeletal 
spicules of Litliistida. Rhizomoriua : a, b, Seliscothou ; c, Cmmidia- 
striun. Tetracladina : d, Aulocopium megamorina ; e, f, Dorydcrma; 
g, Carterclla. Eutaxicladina: h, Astylospo)i{iia. a, b, c, d, h, enlarged 
40 diam. ; e, 26 diam. ; /, g, 20 diam. (After Hinde.) 
Fig. 13. — Fossil sponge spicules : Silicispongiae, Tetractinellida. Skeletal 
(a-c) and dermal (f-i) spicules of Lithistida. Eutaxicladina : a, 
Mastosia. Anomocladina : b, Cyliiulrophyma. Tetracladina : c, d, 
Callopcgma ; e, Plinthosella. e, enlarged 26 diam. ; the rest 40 diam. 
(After Hinde.) 
cladina (Fig, 13 i) ; C[i/iiitdrophj/ma is common in Upper 
Jurassic rocks. Megamorina (Silurian to Recent) : desrnas 
relatively large, curved, branclung rods, either intertwining 
or joined as in Eutaxicladina (Fig. 12 e, f, g) ; Dorgdcrma 
(Fig. lb b) is abundant in the Upper Chalk. Rhizomorina 
(Cambrian to Recent) : desma small, usually elongate, curved, 
with irregular branches ; these end in minute facets, wliich 
Gallery X. 
